Effects of dietary supplementation with synthetic vitamin D-3 and 25-hydroxycholecalciferol on blood calcium and phosphate levels and performance in laying hens

We investigated the effects of different dietary vitamin D regimen on selected blood parameters in laying hens. Supplementation with vitamin D-3 only was compared with a combination of vitamin D-3 and its metabolite 25-hydroxy-cholecalciferol (25(OH)D-3). Blood concentrations of total calcium, phosphate and 25 (OH)D-3 were determined. Four thousand one-day-old LSL chicks were split in two treatment groups and distributed to eight pens. The control group was given a commercial animal diet containing 2800 IU synthetic vitamin D-3 in the starter feed and 2000 IU synthetic vitamin D-3 in the pullet feed. The experimental group was fed the same commercial diet in which half the synthetic vitamin D-3 content had been substituted with 25(OH)D-3 (Hy center dot D (R)). At 18 weeks of age, pullets were transferred to the layer house. At the ages of 11, 18 and 34 weeks, between 120 and 160 blood samples were collected from both the control and the experimental groups, respectively. The experimental group had higher levels of 25 (OH)D-3 than the control group at all three ages. Serum calcium levels did not differ between the treatment groups at any age. With the onset of laying, calcium levels rose significantly. Whereas blood serum concentration at 18 weeks was 3 mmol/L in both treatment groups, it increased to 8.32 mmol/L in the control group and to 8.66 mmol/L in the experimental group at week 34. At weeks 11 and 34, phosphate was significantly lower in the experimental group. In conclusion, HyD (R) significantly affected serum phosphate and 25(OH)D-3 levels. No effects of (25(OH)D-3 supplementation on performance, shell quality and fractures of keelbones were found.